I have 1998 infiniti qx4 my first 4 wheel drive about three months ago now I checked the oil and needed a quart and a half it was coal black,and opened the radiator cap the rubber ring looks like its eroading there is appears to be black specks in it. Oh also there was a whining sound that started about a month after I bought it the car looked it over and said it was a pulley or alternator.its my only vehicle that runs I need help.

Your title says there's oil in the radiator but the body of your question doesn't say that. Are you just leaking oil from the engine? It's a '98, I'm sure it has decent mileage on it and surely there must be some leaks or at least minor blow-by. Before you checked it and it was 1 1/2 quarts low... when was the last time you had known it was full?

Maybe you should just start by flushing the radiator, getting a new radiator cap, and doing an oil change. Then just keep your eye on the fluids and see how it all goes.

Does that vehicle have a transmission oil cooler incorporated into the cooling system? If so, the problem may not be as serious as it first appears.
When was the oil last changed? How long did it take to become that low on oil? These problems are not necessarily related.
If it is high mileage that may be normal oil consumption considering the amount of wear. Depends on when oil was added last etc.

I would change all fluids and filters on the car. Then, I would keep a Maintenance Log on the vehicle and perform all procedures called for in the Owner's Manual.